2002 CADILLAC SEVILLE STS

Typical onset: 80,000-150,000 mi

Symptoms: White smoke from exhaust on cold start, Coolant loss with no visible leaks, Overheating under load or in traffic, Coolant in oil (milky dipstick) in severe cases, Check engine light with P0128 or misfire codes

Fix: The aluminum block threads strip, allowing head bolts to pull out under pressure. Proper repair requires timesert installation (helicoil won't hold), head resurfacing, and new gaskets. 18-24 labor hours for both heads. Many shops won't touch it—you need a Northstar-experienced tech or specialty shop.

Estimated cost: $3,500-6,000

Typical onset: 100,000-180,000 mi

Symptoms: Burning through 1+ quart every 500-1000 miles, Blue smoke on acceleration, Low oil pressure warning, Knocking or ticking from lower engine, Catastrophic rod bearing failure if oil runs low

Fix: Worn piston rings and valve seals cause oil burning. If driven low on oil, rod bearings and main bearings fail. Requires complete engine rebuild or replacement. 28-35 hours for full rebuild including machine work, or 16-20 hours for used engine swap.

Estimated cost: $5,000-8,500

Typical onset: 60,000-120,000 mi

Symptoms: Transmission fluid puddle under front of vehicle, Transmission slipping or delayed engagement, Overheating transmission (burning smell), Harsh shifts after fluid loss

Fix: The steel lines rust through where they connect to the radiator or at frame mount points. Replace both cooler lines preventatively—one fails, the other is close behind. 2-3 hours labor. If caught early before transmission damage, relatively cheap fix. If transmission ran low and burned clutches, add $2,000-3,500 for rebuild.

Estimated cost: $350-600

Typical onset: 90,000-140,000 mi

Symptoms: Harsh clunk when shifting from Park to Drive/Reverse, Vibration at idle in gear, Excessive driveline movement felt during acceleration, Visible separation of rubber in mount on inspection

Fix: The hydraulic transmission mount fails, allowing excessive drivetrain movement. Requires lifting engine/trans assembly slightly for access. 2.5-3.5 hours labor. Use OEM or quality aftermarket—cheap mounts fail within a year.

Estimated cost: $400-650

Typical onset: 70,000-130,000 mi

Symptoms: No-start condition with cranking but no fire, Intermittent stalling while driving, Check engine light with P0335 or P0336 codes, Dies and won't restart until cooled down

Fix: Sensor located behind starter on the Northstar. Requires removing starter for access. Heat soak from engine causes sensor failure. 1.5-2 hours labor. Always replace with AC Delco—aftermarket sensors fail frequently.

Estimated cost: $250-400

Typical onset: 80,000-150,000 mi

Symptoms: Fuel smell in garage or when parked, Visible fuel wetness on top of fuel tank, Hard starting after sitting overnight, Check engine light with fuel trim codes

Fix: The plastic fuel filter housing on top of the tank cracks or the quick-connect fittings leak. Requires dropping the fuel tank. 3-4 hours labor. Replace filter assembly and inspect all fuel lines while tank is down.

Estimated cost: $450-750